AK Dewdney and Project Achilles
The first clues about what happened on 9/11 came from phone calls made by the passengers on board the four flights, describing hijackers who stabbed others, broke into the cockpit, and used mace and the threat of bombs to maintain control. But there are those who say these calls were faked, or at least couldn't have happened as described. The reason? It's claimed that mobile phones simply don't work at altitude, with it being virtually impossible to make calls about 8,000 feet.
The science behind this comes courtesy of AK Dewdney's "Project Achilles", where he tried making cell phone calls while flying over London, Ontario, then reported on the results.
End of the story? Not necessarily. Note this description of the route Dewdney flew in part #2 of the experiment, for instance:
Dewdney is making calls within a short distance of the city centre, then. It's unclear how many mobile phone base stations would be within this area, but he describes it as "richly supplied", and that would make sense. Networks must install more base stations in a populated area because each one can only support so many simultaneous calls; the higher the surrounding mobile-using population, the more base stations you need.
There's a consequence to this, though, as Ericsson spell out.
In other words, base stations in urban areas use less power, and therefore have a shorter range, than those out in the country. What is the potential range? We couldn't find a US figure (email if you can), however a German page at least offers a starting point:
100 metres to 15 kilometres is around 328 feet to 9.3 miles: an enormous difference. If Dewdney were flying over base stations with a range at the lower end of this scale then it's not at all surprising that he had problems making calls. However, this does not prove that calls could not have been made from a plane flying over rural areas, where the base stations need to use more power, and so have a greater range.
We've also seen a suggestion that the phones Dewdney used may have been less likely to work than those available on 9/11. We have no idea if this is true or not, but it's a point to consider:
However, even with these issues, Dewdney does not (as many people paraphrase him) simply say that calls above 8,000 feet are impossible. In fact he specifically says they can (for at least one type of cellphone -- please, read the full link for clarification of this if you've not done so already):
Whether his results are "optimal" is open to question, as we've seen, however here he is suggesting there's a 1 in a hundred chance of success of making a call. So how do we get to "impossible"? Like this:
What Dewdney is saying is that the probabilites must be multiplied together. If the chance of you winning a basic prize on the lottery is one in ten, for instance, then the probability of you winning twice with two tickets is 10 x 10 = 1 in 100.
When we're dealing with unrelated and independent events, like the lottery tickets, this is correct. But the phone calls were not independent, they relied on precisely the same set of circumstances. If a 9/11 plane were in the right position, in relation to a powerful base station, for the calls to take place, then it was in the right position for everyone on the plane (who had a mobile which could use that base station). At any given moment, either all this group of people could get through, or none of them. Therefore the chance of 2 people getting through remains close to 1 in 100, even with Dewdneys flawed conditions, not the 1 in 10,000 he claims.